Semiconductors electron mobility

Semiconductor Electron mobility (m V s ) Hole mobility (rtfV s )... 

Where b is Planck s constant and m and are the effective masses of the electron and hole which may be larger or smaller than the rest mass of the electron. The effective mass reflects the strength of the interaction between the electron or hole and the periodic lattice and potentials within the crystal stmcture. In an ideal covalent semiconductor, electrons in the conduction band and holes in the valence band may be considered as quasi-free particles. The carriers have high drift mobilities in the range of 10 to 10 cm /(V-s) at room temperature. As shown in Table 4, this is the case for both metallic oxides and covalent semiconductors at room temperature. 

Optoelectronic components produced by CVD include semiconductor lasers, light-emitting diodes (LED), photodetectors, photovoltaic cells, imaging tubes, laser diodes, optical waveguides, Impact diodes, Gunn diodes, mixer diodes, varactors, photocathodes, and HEMT (high electron mobility transistor). Major applications are listed in Table 15.1.El... 

Zinc oxide is a thoroughly studied typical semiconductor of n-type with the width of forbidden band of 3.2 eV, dielectric constant being 10. Centers responsible for the dope electric conductivity in ZnO are provided by interstitial Zn atoms as well as by oxygen vacancies whose total concentration vary within limits 10 - 10 cm. Electron mobility in monocrystals of ZnO at ambient temperature amounts to 200 cm -s". The depth of donor levels corresponding to interstitial Zn and oxygen vacancies under the bottom of conductivity band is several hundredth of electron volt [18]. 

The fundamental physical properties of nanowire materials can be improved even more to surpass their bulk counterpart using precisely engineered NW heterostructures. It has been recently demonstrated that Si/Ge/Si core/shell nanowires exhibit electron mobility surpassing that of state-of-the-art technology.46 Group III-V nitride core/shell NWs of multiple layers of epitaxial structures with atomically sharp interfaces have also been demonstrated with well-controlled and tunable optical and electronic properties.47,48 Together, the studies demonstrate that semiconductor nanowires represent one of the best-defined nanoscale building block classes, with well-controlled chemical composition, physical size, and superior electronic/optical properties, and therefore, that they are ideally suited for assembly of more complex functional systems. 

Electron mobility, in direct gap semiconductors, 22 143-144 Electron paramagnetic resonance (epr), 17 418... 

Field-effect transistors (FETs) Heterojunction bipolar transistors (HBTs) High electron mobility transistors (HEMTs) Metal oxide semiconductor FETs (MOSFETs) Single-electron transistors (SETs) Single-heterojunction HBTs (SH-HBTs) Thin-film transistors (TFTs) hydrogenated amorphous silicon in, 22 135... 

Both electrons and holes are mobile charge carriers in semiconductors. The mobile charge carrier whose concentration is much greater than the other is called the majority carrier, and the minority carrier is in much smaller concentrations. In n-type semiconductors, the mcgority carriers are electrons in the conduction band and the minority carriers are holes in the valence band. The product of the concentrations of majority and minority carriers (electrons and holes) in a semiconductor of extrinsic type (containing impurities) equals the square of the concentration of electron-hole pairs, ni, in the same semiconductor of intrinsic type (containing no impurities) ... 

Electrical conductivity is due to the motion of free charge carriers in the solid. These may be either electrons (in the empty conduction band) or holes (vacancies) in the normally full valence band. In a p type semiconductor, conductivity is mainly via holes, whereas in an n type semiconductor it involves electrons. Mobile electrons are the result of either intrinsic non-stoichiometry or the presence of a dopant in the structure. To promote electrons across the band gap into the conduction band, an energy greater than that of the band gap is needed. Where the band gap is small, thermal excitation is sufficient to achieve this. In the case of most iron oxides with semiconductor properties, electron excitation is achieved by irradiation with visible light of the appropriate wavelength (photoconductivity). 

Katz FIE, Lovinger AJ, Johnson J, Kloc C, Siegrist T, Li W, Lin Y-Y, Dodabalapur A (2000) A soluble and air-stable organic semiconductor with high electron mobility. Nature 404 478 81... 

Silicon has a density of 2.40 g/cm. (a) What is the concentration of the silicon atoms per cubic centimeter (b) Phosphorus is added to the silicon to make it an n-type semiconductor with a conductivity of 1 mho/cm and an electron mobility of 1700 cm /V-s. What is the concentration of the conduction electrons per cubic centimeter ... 

Fig. 2. Electron drift velocities as a function of electric field for A, GaAs and B, Si The gradual saturation of curve B is characteristic of all indirect semiconductors. Curve A is characteristic of direct gap semiconductors and at low electric fields this curve has a steeper slope which reflects the larger electron mobility. The peak in curve A is the point at which a substantial fraction of the electrons have gained sufficient energy to populate the indirect L minimum which has a much larger electron-effective mass than the T minimum. Above 30 kV/cm (not shown) the drift velocity in Si exceeds that in...

Electrical Properties. Generally, deposited thin films have an electrical resistivity that is higher than that of the bulk material. This is often the result of the lower density and high surface-to-volume ratio in the film. In semiconductor films, the electron mobility and lifetime can be affected by the point defect concentration, which also affects electromigration. These effects are eliminated by depositing the film at low rates, high temperatures, and under very controlled conditions, such as are found in molecular beam epitaxy and vapor-phase epitaxy. 

Semiconductor Energy Gap (eV) Electron Mobility. ve (cm V ls l) Hole Mobility, v (etirV s-1)... 

New physics such as the fractional quantum Hall effect has emerged from non-magnetic semiconductor heterostructures. These systems have also been a test bench for a number of new device concepts, among which are quantum well lasers and high electron mobility transistors. Ferromagnetic 111-Vs can add a new dimension to the III-V heterostructure systems because they can introduce magnetic cooperative phenomena that were not present in the conventional III-V materials. 

It accounts for the effects of the difference of work function of the gate metal (j>M and silicon 0Si and any residual charges gss that exist in the gate insulator. 0S is the surface potential of the semiconductor. The mobile electron charge in the surface inversion layer is then given by... 

The most dramatic example of the use of functionalization to tune the properties of an organic semiconductor is found in perfluoropentacene 41 (Scheme 3.9) [53]. Perfluoropentacene has a strongly shifted LUMO, evidenced by lowering of the reduction potential by more than 700 mV. The fluorinated compound adopts a herringbone packing in the crystal that is very similar to that of the parent acene. Top-contact FET devices made from evaporated 41 had an electron mobility of 0.11 cm2 V-1 s 1, demonstrating the change from p-type to n-type behavior. 

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